1. Field of the Invention
The present invention is directed to a conveyor system. More particularly, this invention concerns a pallet conveyor system in which individual pallets are independently conveyed along a fixed track or way to and from one or more workstations.
2. Reference to Related Art
The use of conveyor systems for transporting workpieces to and from workstations is known in the art. Indeed, a wide variety of conveyor designs have been developed or adapted for use in connection with the automatic transport of workpieces during manufacturing operations. One particular category of these conveyor systems utilizes a system of pallets that are driven along a track. Typically, in systems of this type, a workpiece is supported on a pallet that is then propelled into and out of at least one workstation.
One reference relevant to this category of conveyor systems is U.S. Pat. No. 4,388,684 to Peck. The ""684 reference discloses a pallet conveyor that includes a longitudinally extending pallet that is supported upon a track. A plurality of rotary drives are spaced along the track and engage the pallet to transport the pallet along the track.
U.S. Pat. No. 4,987,834 issued to Peck, Jr. et al. also discloses a conveyor with self-propelled pallets. More particularly, the ""834 reference discloses a conveyor system that includes a plurality of pallets supported upon a track. Each of the pallets includes a drive motor and a control system capable of queuing the pallets into position.
While these and other prior art pallet systems permit transport of a pallet carrying a workpiece along a track, the precise alignment of the workpiece in the workstation remains problematic. Indeed, while the ""834 reference discloses the use of a plurality of pallets along the track, each pallet must be clamped into position at the workstation before workstation operations may begin. Furthermore, problems with pallet precision as well as pallet speed necessarily increase as the weight of the workpiece increases.
Therefore, there is a need in the art for a pallet conveyor system having a drive means that permits highly accurate and reproducible placement of a workpiece at a workstation and is capable of transporting all manner of workpieces without a resulting decrease in performance. Additionally, the conveyor system should include means for safe operation of the conveyor system and the capability to easily and effectively communicate with and control individual pallets in the system.
A pallet conveyor system of the present invention includes a rail assembly and a pallet assembly. The rail assembly preferably includes a pair of spaced apart and parallel conveyor supports, each of the conveyor supports having a support rail mounted thereon. The rail supports each include a cylindrical rail that functions as a track or way for the pallet assembly. Preferably, at least one of the rail supports includes a number of parallel transmission bars that arc used to transmit electrical power to the pallet assembly. An intermediate support is preferably positioned between the rails and includes on one side a rack and, on an opposite side, a removable and repositionable stop bar. A data coupler is preferably secured to at least one of said rail supports and is adapted to communicate with and provide any necessary command instructions to the pallet assembly. Command instructions are preferably provided while the pallet assembly is stopped at a workstation. However, it should be appreciated that commands may also be transmitted to the pallet assembly through the data coupler while the pallet is moving along the track. Alternatively, commanding instructions may be transmitted to the pallet assembly through the transmission bars or through radio or another manner of transmission that is known in the art.
The pallet assembly includes a body having a longitudinal extending frame and a base. Preferably, the pallet is supported on the rails of the rail assembly by a plurality of roller bearings. A drive system for the pallet assembly, that permits both forward and reverse motion for the pallet, engages the rack of the rail assembly to propel the pallet assembly along the rails. A trolley assembly is secured to the frame of the body and includes a housing and a number of brushes that are biased to contact the transmission bars.
Cueing of the pallet assembly into a workstation is preferably controlled by use of a pair of sensors. Specifically, a first sensor and second sensor are secured to the pallet assembly and are positioned to detect the stop bar as the pallet moves along the rails. As the first sensor detects the stop bar, the pallet assembly is slowed. Thereafter, as the second sensor detects the stop bar, the pallet assembly is stopped. Therefore, it should be apparent that a mere repositioning of the stop bar will result in the pallet assembly being easily and precisely stopped at any location along a conveyor line without the need to reprogram the pallet assembly. Preferably, the pallet assembly is restated along the rails by the transmission through the data coupler (or the like) of a start signal. Preferably, the start signal is manually activated by the user, as the user is clear of the conveyor system.